In today's market the consumer is aware of quality and the benefits of purchasing a quality product. Quality combined with a reasonable or competitive price of a product creates value. The paint finish of particular vehicles, such as passenger cars or trucks, plays a major role in convincing a potential customer that quality of the product is good. If the aesthetic quality of the product is easily inspected by a customer and is satisfactory, the customer often assumes that the entire product must be of the same quality level.
To obtain a high quality process, the paint application industry resorts to the use of sophisticated and newly-developed equipment for applying and processing the paint finish. The research, development and marketing of some equipment areas have accelerated to meet the need for higher quality paint finishing, such as robotic applicators which were recently made more accurate by the use of improved electric robots in lieu of the prior hydraulic robots or manual spray persons, intelligent conveyor systems which locate the object to be sprayed more precisely for the automatic spray equipment, the use of flexible products and infra-red ovens which can cure or dry the paint applied to these products without melting the substrate, etc. An area which has not accelerated in the paint application process is the paint circulation system to deliver paint in large paint application processes. The current technologies are not geared toward the paint products themselves, many of the paint products have been newly-developed to meet environmental issues, for example, water based paint products.
The current technologies of paint circulation systems are not geared toward efficiency and are not cost-effective with respect to operating expenses. The current designs are expensive to initially purchase and install. The current designs are also complex and difficult to operate in the manner necessary to keep the same parameters of the system on a daily basis which is required to achieve consistent quality levels. The current designs also require large volumes of hazardous materials to be used and disposed of annually to clean the system.
The following describes a typical previously-known paint circulation system. For instance, in a high-volume paint application process, vehicles or parts thereof travel through various spray booths or enclosures by means of a conveyor system. As these parts travel past the paint application equipment, the parts are coated with the appropriate paint products and paint colors. Often times several different colors are applied at the same spray booth with the same application equipment throughout the course of the day or even within a single 30 minute time period. In many paint application processes, a vehicle passing through the booth will be painted one color, while the vehicle next in line is to be painted a different color and the vehicle after that is to be painted yet another color and so on. To accomplish this task efficiently all necessary paint colors are circulated to these spray booths and remain available for use. Each color has its own system and piping network. At each application point in the spray booth, each piping network has an outlet port connected to an automated valve, which in turn is connected to a manifold typically called a "color change valve stack". Also connected to this color change manifold is a purge or cleaning solvent. By automatic sequencing, a single valve is opened on this manifold and the related color is provided to the application equipment and thus applied to the vehicle or part. Upon completion of painting that vehicle a specific color, the valve is automatically closed and the cleaning solvent valve is opened to rinse out the last color in preparation for the next vehicle color to be applied. As the next vehicle passes by the application equipment, the next appropriate color valve is opened to paint the new color. This automatic sequence is commonly referred to as a "color change". This procedure allows painting vehicles passing through the spray booths closely together to be different colors without the need to stop the conveyed vehicles to manually clean application equipment.
To make all paint colors available to all spray booths and equipment at all times, each color is contained in a paint circulation system. As high volumes of various colors of paint are used, the requirement to contain large volumes of product on site exist. These paint products range with respect to hazardous material ratings from classifications of combustible, which is typical for waterborne paint products, to flammable liquids, which is typical for solvent-based products. For safety reasons, these large volumes of material are stored and supplied from an environment which has specific safety guidelines to protect personnel and the facilities. As mentioned, the products are stored and supplied from this specific location known in the industry as a "paint mix room or building".
Some of the requirements to keep this paint mix building safe are: all electrical equipment is explosion-proof rated, all electrical power sources are installed in an explosion-proof class enclosure, grounding mats are installed to prevent static electricity, fresh air is circulated constantly, explosion-proof walls are constructed and blow out or relief panels are installed in case of an actual explosion, exotic fire extinguishing equipment is usually installed, spark-proof floors are provided, relative humidity is controlled to 50% or above which requires relative humidification equipment, and several other considerations must be in effect to meet the codes concerning hazardous environments. It is for this reason that the paint products are stored in a specific or centralized location. Explosion-proof relief systems are designed to relieve building pressure in the event of an explosion by actually allowing these relief panels to blow off and become detached from the remaining portion of the building. For this reason the paint mix building is located on an outside wall of the main facility, or may even be totally separate from the main facility. The paint mix building is therefor usually a great distance from the various paint spray booths where the paint is to be applied to the vehicle or parts. The fact that the paint spray booths are typically scattered throughout the manufacturing and painting facilities further increases this distance. Furthermore, the spray booths are generally quite long and each booth is located some distance apart from each other.
In the past, a paint circulation system for plants which require several colors to be available at the application areas would result in the following type of paint circulation system. Each color would be contained in its own tank at a pumping station located in the paint mix room. Paint material would be piped through piping, usually stainless steel, the long distance from the paint mix building to the paint spray booth application areas. After arriving at the paint spray booths the piping circles each spray booth to provide paint to application equipment on each side of the spray booth for each applicable booth. This piping is typically called the "high pressure supply line". After this high pressure supply line has provided paint to the most remote spray booth application points, this piping returns to the tank in the paint mix building. This piping is typically referred to as the "high pressure return line". Just prior to entering the tank, a back pressure regulator, or flow control device, is used to adjust the volume of paint returning. This controls the velocity inside of the circulating paint line. Paint products are circulated at predetermined speeds or velocities to keep by-products from separating from the mixture. The industry standard for paint velocity circulated within a pipeline is 60 feet per minute.
To ensure circulation of paint products in all areas of the circulation system, such as the station drop tubes to each actual application equipment or manual spray station, various circulation system types or configurations have been used. Some system variations may add additional piping or equipment to the overall system, however, in all system variations supply and return main piping headers are required.
All types of prior known paint circulation systems which deliver paint from a remote paint mix room or building to various paint spray booths and application equipment use points have common equipment, such as supply and return pipe headers. The length of the continuous pipe header from the mix room to and around all applicable spray booths, and the return pipe header back to the mix room is extremely long. In many of today's installations in the automotive and other industries, this pipeline for each color exceeds one mile in length. The pumping station must provide enough pressure to satisfy the most remote application point from the paint mix building, sometimes referred to herein as a second pressure for comparison purposes. Due to the great distance and the viscosity of paint, this piping header must be large in diameter to decrease the amount of pressure loss experienced while conveying the paint through a pipeline of this distance. It is typical for this pipe header to be a two-inch diameter Schedule 5 pipe header or even larger. With this size pipe and having a pipe length in excess of one mile, the pump source may be required to pump paint at a pressure in the range of 250 pounds per square inch in order to maintain the desired industry standard velocity of 60 feet per minute minimum, and provide the required application spray pressure at the most remote paint application point. Therefore, the larger the paint high pressure supply header, the high pressure return header and, when applicable, the additional low pressure return header, the greater the volume of paint is required to maintain this velocity.
In summary, all types of previously known paint circulation systems require large diameter piping to reduce pressure drop and large volumes of paint supplied to the piping to meet minimum velocity requirements. The end result of these requirements can be summarized as five problem areas. First, these prior known systems create quality problems related to the paint application process. Second, the initial purchase price of these large size components and piping are expensive, and the installation labor cost to install a large and heavy system is expensive. Third, operational cost of these large systems is extremely expensive. Fourth, these large systems generate an enormous amount of hazardous waste, and therefore create environmental concerns, in addition to the economic concerns associated with disposing of hazardous waste. Fifth, these large systems are difficult to control in a manner that will produce the high quality finished product desired by present-day manufacturers.